/*********************************************************************************
 *      Copyright:  (C) 2025 LingYun<iot25@lingyun>
 *                  All rights reserved.
 *
 *       Filename:  socket_server_fork.c
 *    Description:  This file 
 *                 
 *        Version:  1.0.0(06/03/25)
 *         Author:  LingYun <iot25@lingyun>
 *      ChangeLog:  1, Release initial version on "06/03/25 22:06:37"
 *                 
 ********************************************************************************/
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <getopt.h>
#include <ctype.h>

void print_usage(char *progname)
{
	printf("%s usage:\n",progname);
	printf("-p(--port): sepcify server listen port.\n");
	printf("-h(--help): print this help information.\n");
	return;

}
int main(int argc, char **argv)
{
	int					sockfd = -1;
	int					rv = -1;
	struct sockaddr_in	servaddr;
	struct sockaddr_in	cliaddr;
	socklen_t			len;
	int					port = 0;
	int					clifd;
	int					ch;
	int					on = 1;
	pid_t				pid;

	struct option			opts[] = {
		{"port", required_argument, NULL, 'p'},
		{"help", no_argument, NULL, 'h'},
		{NULL, 0, NULL, 0}
	};

	while( (ch=getopt_long(argc, argv, "p:h", opts, NULL)) != -1)
	{
		switch(ch)
		{
			case 'p':
				port=atoi(optarg);
				break;
			case 'h':
				print_usage(argv[0]);
				return 0;
		}
	}

	if( !port )
	{
		print_usage(argv[0]);
		return 0;
	}

	sockfd=socket(AF_INET, SOCK_STREAM, 0);
	if(sockfd < 0)
	{
		printf("Create socket failure: %s\n", strerror(errno));
		return -1;
	}
	printf("Create socket[%d] successfully!\n", sockfd);

	setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));

	memset(&servaddr, 0, sizeof(servaddr));
	servaddr.sin_family=AF_INET;
	servaddr.sin_port=htons(port);
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	
	rv=bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
	if(rv < 0)
	{
		printf("Socket[%d] bind on port[%d] failure: %s\n", sockfd, port, strerror(errno));
		return -2;
	}
//开始监听
	listen(sockfd, 13);
	
	printf("Start to listen on port [%d]\n", port);
	
	while(1)
	{
		printf("Start accept new client incoming...\n");
		len = sizeof(cliaddr);//初始化len

		clifd=accept(sockfd, (struct sockaddr *)&cliaddr, &len);
		
		if(clifd < 0)
		{
			printf("Accept new client failure: %s\n", strerror(errno));
			continue;
		}
		
		printf("Accept new client[%s:%d] successfully\n", inet_ntoa(cliaddr.sin_addr),
				ntohs(cliaddr.sin_port));
		//创建子进程
		pid = fork();
		
		if( pid < 0 )
		{
			printf("fork() create child process failure: %s\n", strerror(errno));
			close(clifd);
			continue;
		}
		else if( pid > 0 )
		{
			/*  Parent process close client fd and goes to accept new socket client again */
			close(clifd);
			continue;
		}
		else
		{
			char buf[1024];
			int i;
		
			printf("Child process start to commuicate with socket client...\n");
			
			close(sockfd); /*  Child process close the listen socket fd */
			
			while(1)
			{
				memset(buf, 0, sizeof(buf));
				rv=read(clifd, buf, sizeof(buf));
				if( rv < 0 )
				{
					printf("Read data from client sockfd[%d] failure: %s\n", clifd,
							strerror(errno));
					close(clifd);
					exit(1);
				}
				else if( rv == 0) 
				{
					printf("Socket[%d] get disconnected\n", clifd);
					close(clifd);
					exit(0);
				}
				else if( rv > 0 )
				{
					printf("Read %d bytes data from Server: %s\n", rv, buf);
				}
				/* 小写转大写 convert letter from lowercase to uppercase */
				for(i=0; i<rv; i++)
				{
					buf[i]=toupper(buf[i]);
				}
				rv=write(clifd, buf, rv);
				
				if(rv < 0)
				{
					printf("Write to client by sockfd[%d] failure: %s\n", clifd,
							strerror(errno));
					close(clifd);
					exit(1);
				}
			} /*  Child process loop */
		} /*  Child process start*/
	}
	close(sockfd);
	return 0;
}
